I'm back again with my poor Rollergames
Long story short, after replacing a burnt coil (#18), I put the game back together and accidentally plugged 2J9 in 5J9. F8 blew and I had now a locked right kicker (#16). I replaced the transistor, pre-transistor and diode but the issue persisted so I added a socket and replaced U17.
Now, the game doesn't boot (+5v LED is on, diagnostic and blanking are off).
It's almost impossible to check due to the clearance between the socket and board but could a solder bridge on that newly installed socket prevent the game from booting?